火星上有水吗?是怎样探测出来的?

据英《新科学家》２００２年６月８日报道 :自２００２年３月以来 ,有大量消息报道 ,说美国ＮＡＳＡ的火星探测器“奥德赛”几乎已肯定探测出火星上存在水冰 ,并指出水冰处于距火星表面仅几厘米的地下 ;有人问 ,ＮＡＳＡ在１９７６年曾发射“海盗２号”在火星着陆 ,那时并没有听说探测到火星上有水 ,现在却这么肯定火星上有水冰 ,这是怎么回事呢？为了弄清究竟 ,于是有许多研究人员开始日以继夜地设计新的火星着陆器 ,都想成为第一个钻穿火星地表并挖出地下水冰的探测器的设计者。其实 ,尽管火星上有水的消息令人振奋 ,但并没有任何证实火星…     

火星上的冰能证明生命存在吗

2008年6月20日,负责"凤凰"号火星探测任务的科学家确认,"凤凰"号在火星上发现的坚硬明亮物质的确是冰冻水。科学家们由此产生疑问,在漫长的历史长河中,火星上的这些冰冻水是否曾融化过·是否诞     

火星生命探测的新进展

据英《新科学家》２００２年４月１３日报道 :科学家最近对地球上生长的岩石进行研究后指出 ,在火星上的岩石中可能存在微生物生长所需的大量能源。对火星表面下存在生命抱有希望的许多科学家认为 ,在火星地表下有液态形式的水 ,因此很可能有生命存在。那么 ,没有液态水是否就根本不可能有微生物呢？研究发现 ,在地球上有些微生物就生活在岩石的深处 ,它们从氢中获得所需的能量而生存 ;氢是由岩石中的铁和水反应产生的。加利福尼亚莫非特菲尔德ＮＡＳＡ埃姆斯研究中心的ＦｒｉｅｄｍａｎｎＦｒｅｕｎｄ曾经认为 ,在地下深处产生的氢很分散的…     

地球生命来自太空陨石

最近，火星探测的热潮激起了大家对探索生命起源的兴趣，科学家在火星上也发现了类似于地球的陨石坑。不少科学家推测，生命可能起源于这些陨石坑。于是，人们又把生命起源的目光投向那些可能撞击地球和火星的彗星和小行星。现在，一种时髦的理论认为，是来自太空的携带有水和其他有机分子的彗星和小行星撞击地球后，才使地球产生了生命。     

“火星勘测轨道器”完美入轨

2006年3月10日，“火星勘测轨道器”成功进入火星轨道。它身怀绝技，携带各种利器，将要解答火星上水和生命的难题。它究竟能够发现什么有价值的线索？人们将拭目以待。[编者按]     

从天体运动的定律到隐藏在宇宙背后的未知定律

宇宙中有各种各样的天体和现象。这些天体和现象是偶然出现的，抑或是在某些自然定律支配下的必然结果？ 科学家通过不断地观测、实验和思考，已经发现了隐藏在宇宙背后的许多“定律”。他们究竟是如何发现这些定律的？恒星和行星乃至宇宙全体究竟要遵循哪些定律？     

火星内部含水量与地球相当

无论在哪里,水都是一个关乎生命的大问题。美国科学家对两块源于火星地幔的陨石进行分析,发现火星内部含水量远远大于过去的估计,其总量与地球内部含水量相当。科学家分析的两块陨石,一块在形成时混合了其他元素,另一块则没有与其他元素混合。然而他们在分析陨石矿物磷灰盐的含水量时,发现两块陨石的含水量没什么差别。这表明,火星在形成时就包含了水,在其发生变化时内层能储水。     

风光无限——世界科技一年回顾

新的发现新的突破 1996年适逢瑞典发明家阿尔弗雷德·诺贝尔逝世100周年。这一年,科学家们继续向自然界深度和广度进军。航天领域:美国航空航天局在30天之内连续两次向火星成功发射了“火星环球勘测者”和“火星探路者”探测器,揭开了人类向火星进军的新篇章。进军地下:大有收获。美国科学家发现地球固体内核比地球旋转速度快,这可能有助于理解地球磁场形成的机理(爱因斯坦认为解释地球磁场是物理学领域难题之一);科学家们还从遗传学角度证实生活在太平洋底近沸点水中的微生物杨氏产甲烷球菌是地球上第三种生命形式。这一发现可能会填补生命诞生和进化过程中的研究空白。     

你好!“火星人”

正火星是否存在生命?1890年,美国天文学家珀西瓦尔·罗威偶然发现在火星表面存在着一些沟壑,类似人工开凿的运河——人们开始怀疑火星生命的存在,大量关于火星人的科幻故事从此风靡1890年,美国天文学家珀西瓦尔·罗威尔利用大型望远镜观测火星,偶然发现在火星表面存在着一些沟壑,这些东西和地球上人工开凿的运河看起来极为相似。人们开始怀疑有火星上存在智慧生命。大量关于"火星人"的科幻故事从此也广为流传。科学家们一直相信火星上有水资源的存在,而且可能是在火星两极或大气高层中以冰雪及水蒸气的形式存在。甚至有许多科学家相信,火星上也可能曾分布有河流和冰川。因为从目前观测到的照片来看,火星上有许多峡谷和沟壑看起     

火星曾经三分之一表面覆盖海洋

科学家利用新软件对火星表面进行分析，发现火星曾有三分之一的表面被海洋覆盖。他们在赤道和中南纬度之间的狭长地带找到了，比以前科学家在火星上发现的、多出1倍多的溪谷，绘制成迄今为止最为详细的火星溪谷图。这张新图是利用卫星数据进行电脑分析产生的，     

Impact origin of sediments at the Opportunity landing site on Mars

Mars Exploration Rover Opportunity discovered sediments with layered structures thought to be unique to aqueous deposition and with minerals attributed to evaporation of an acidic salty sea. Remarkable iron-rich spherules were ascribed to later groundwater alteration, and the inferred abundance of water reinforced optimism that Mars was once habitable. The layered structures, however, are not unique to water deposition, and the scenario encounters difficulties in accounting for highly soluble salts admixed with less soluble salts, the lack of clay minerals from acid-rock reactions, high sphericity and near-uniform sizes of the spherules and the absence of a basin boundary. Here we present a simple alternative explanation involving deposition from a ground-hugging turbulent flow of rock fragments, salts, sulphides, brines and ice produced by meteorite impact. Subsequent weathering by intergranular water films can account for all of the features observed without invoking shallow seas, lakes or near-surface aquifers. Layered sequences observed elsewhere on heavily cratered Mars and attributed to wind, water or volcanism may well have formed similarly. If so, the search for past life on Mars should be reassessed accordingly.     

低温环境下木材细胞中冰晶的形成和传播研究综述

活立木树干内部水分状态对其生理作用的发挥具有重要的影响。低温下,活立木内部水分状态的改变,导致其结构发生变化,这给基于声波技术的活立木材质无损检测带来了一些困难。笔者从宏观和微观角度,综述了树干和木质细胞中冰晶的形成、传播、分布和冰晶体含量的最新研究结果; 讨论了木材细胞内和细胞外水分的冻结模式和冻结行为; 介绍了时域反射技术、低温扫描电镜、差热分析、核磁共振等研究木材内部水冻结过程的方法并比较了各方法的特点。认为当前研究在技术手段、研究对象和深度上仍需进一步拓展,未来应重点以活立木树干及枝干为对象,利用多种手段加强原位检测,对冰晶形成原因、扩展过程及产生结果进行系统研究。通过对低温木材中冰晶的形成和传播机制的综合分析,可为后续开展低温活立木无损检测和树木抗寒性研究提供参考。     

Evidence for recent climate change on Mars from the identification of youthful near-surface ground ice

Ground ice in the crust and soil may be one of the largest reservoirs of water on Mars. Near-surface ground ice is predicted to be stable at latitudes higher than 40 degrees (ref. 4), where a number of geomorphologic features indicative of viscous creep and hence ground ice have been observed. Mid-latitude soils have also been implicated as a water-ice reservoir, the capacity of which is predicted to vary on a 100,000-year timescale owing to orbitally driven variations in climate. It is uncertain, however, whether near-surface ground ice currently exists at these latitudes, and how it is changing with time. Here we report observational evidence for a mid-latitude reservoir of near-surface water ice occupying the pore space of soils. The thickness of the ice-occupied soil reservoir (1-10 m) and its distribution in the 30 degrees to 60 degrees latitude bands indicate a reservoir of (1.5-6.0) x 104 km3, equivalent to a global layer of water 10-40 cm thick. We infer that the reservoir was created during the last phase of high orbital obliquity less than 100,000 years ago, and is now being diminished.     

Implications for hydrologic processes on Mars from extensive bedrock outcrops throughout Terra Meridiani

Grey haematite was recently detected in the Terra Meridiani region of Mars by the Thermal Emission Spectrometer onboard the Mars Global Surveyor spacecraft. The formation of haematite on Earth often requires liquid water to be present for long periods of time, making this an important target for deciphering the history of water on Mars. The Mars Exploration Rover Opportunity landed in Meridiani early in 2004 and has since discovered light-toned bedrock outcrops rich in chemical and textural signatures of long-term water interaction locally at the landing site. Here I use remote sensing data to show that the light-toned outcrops at the landing site are not a local phenomenon. Instead, they are observable throughout the haematite-bearing plains in both visible and thermal infrared remote sensing data. Moreover, the light-toned material outcrops around much of the margin and is mappable for hundreds of kilometres to the north, east and west of the plains. I infer that 3 x 10(5) km(2) of this material is exposed over 20 degrees of longitude, indicating the extended presence of surface or near-surface water over a large region of Mars.     

蓄冰冷机容量的确定

针对在设计蓄冰工程时普遍存在优化蓄冷比来确定蓄冰主机容量的做法和确定蓄冰工况的问题，提出蓄冰冷机的蓄冰运行工况应根据制冷机组的类型和拟采用的蓄冰方式来确定，通过分析计算给出了蓄冰主机在全蓄冷模式、部分蓄冷冷机优先模式、部分蓄冷释冷优先等3种控制模式下确定冷机容量的计算式，并得出了在不同的控制模式下冷机的容量不受蓄冷比影响的重要结论，说明了蓄冰工况和冷机容量的正确选定对合理地设计蓄冰系统有非常重要的作用，并用工程实例做了详细的分析说明。     

Perennial water ice identified in the south polar cap of Mars

The inventory of water and carbon dioxide reservoirs on Mars are important clues for understanding the geological, climatic and potentially exobiological evolution of the planet. From the early mapping observation of the permanent ice caps on the martian poles, the northern cap was believed to be mainly composed of water ice, whereas the southern cap was thought to be constituted of carbon dioxide ice. However, recent missions (NASA missions Mars Global Surveyor and Odyssey) have revealed surface structures, altimetry profiles, underlying buried hydrogen, and temperatures of the south polar regions that are thermodynamically consistent with a mixture of surface water ice and carbon dioxide. Here we present the first direct identification and mapping of both carbon dioxide and water ice in the martian high southern latitudes, at a resolution of 2 km, during the local summer, when the extent of the polar ice is at its minimum. We observe that this south polar cap contains perennial water ice in extended areas: as a small admixture to carbon dioxide in the bright regions; associated with dust, without carbon dioxide, at the edges of this bright cap; and, unexpectedly, in large areas tens of kilometres away from the bright cap.     

High-resolution subsurface water-ice distributions on Mars

Theoretical models indicate that water ice is stable in the shallow subsurface (depths of <1-2 m) of Mars at high latitudes. These models have been mainly supported by the observed presence of large concentrations of hydrogen detected by the Gamma Ray Spectrometer suite of instruments on the Mars Odyssey spacecraft. The models and measurements are consistent with a water-ice table that steadily increases in depth with decreasing latitude. More detailed modelling has predicted that the depth at which water ice is stable can be highly variable, owing to local surface heterogeneities such as rocks and slopes, and the thermal inertia of the ground cover. Measurements have, however, been limited to the footprint (several hundred kilometres) of the Gamma Ray Spectrometer suite, preventing the observations from documenting more detailed water-ice distributions. Here I show that by observing the seasonal temperature response of the martian surface with the Thermal Emission Imaging System on the Mars Odyssey spacecraft, it is possible to observe such heterogeneities at subkilometre scale. These observations show significant regional and local water-ice depth variability, and, in some cases, support distributions in the subsurface predicted by atmospheric exchange and vapour diffusion models. The presence of water ice where it follows the depth of stability under current climatic conditions implies an active martian water cycle that responds to orbit-driven climate cycles. Several regions also have apparent deviations from the theoretical stability level, indicating that additional factors influence the ice-table depth. The high-resolution measurements show that the depth to the water-ice table is highly variable within the potential Phoenix spacecraft landing ellipses, and is likely to be variable at scales that may be sampled by the spacecraft.     

冰区海洋平台静态冰载荷概率特性分析

基于Monte Carlo法 ,对冰区海洋平台静态冰载荷的概率特性进行了分析。在平台设计评估载荷的计算中引入广义冰载荷“当量冰力”的概念 ,并用此概念对冰厚和冰强度的联合作用进行了评估。以渤海辽东湾 4个典型台站为例 ,分析了静态冰载荷主要影响因素的概率特性 ,给出了这几个台站附近海域当量冰力的概率分布参数 ,并定量分析了冰厚和气温对当量冰力的影响。模拟结果表明 ,应用Weibull分布描述概率当量冰力是可行的。此外 ,采用多年一遇的极值条件下冰参数组合求得的当量冰力值比Monte Carlo模拟结果保守得多 ,在工程应用中 ,可采用当量冰力作为平台设计载荷的基础。     

引黄入晋工程申同嘴水库冬季输水安全性分析

为给万家寨引黄入晋工程中中同嘴水库是否采取保温措施提供决策依据,针对水库水温的变化情况建立了基于冰屑形态的水体结冰时间计算模型和基于冰盖形态的出库水温计算模型,计算了水库水体的结冰时间和出库水温．结果表明：库水结冰时间取决于库水位和入库水温,其中库水位影响较大;在形成有效冰盖的状态下,不采取保温加盖措施也能保证冬季输水安全．     

Possible presence of high-pressure ice in cold subducting slabs

During the subduction of oceanic lithosphere, water is liberated from minerals by progressive dehydration reactions and is thought to be critical to several geologically important processes such as island-arc volcanism, intermediate-depth seismicity and chemical exchange between the subducting lithosphere and mantle. Although dehydration reactions would yield supercritical fluid water in most slabs, we report here that the stable phase of H2O should be solid ice VII in portions of the coldest slabs. The formation of ice VII as a dehydration product would affect the generation, storage, transport and release of water in cold subduction zones and equilibrium conditions of dehydration would shift, potentially affecting the depths of seismogenesis and magmagenesis. Large amounts of pure ice VII might accumulate during subduction and, as a sinking slab warms, eventual melting of the ice would release large amounts of water in a small region over a short period of time, with a significant positive volume change. Moreover, the decreasing availability of fluid water, owing to the accumulation of ice VII and its subsequent reaction products in a cooling planetary interior (for example, in Mars or the future Earth), might eventually lead to a decline in tectonic activity or its complete cessation.